This invention is directed to a surface covering, and more particularly to a floor covering product in which a wearlayer composition, preferably an acrylated urethane composition is coated onto a polyvinyl chloride (PVC) or vinyl composition film, preferably a rigid vinyl film, and cured with low energy electron beam (EB) radiation to form a wearlayer/film composite, prior to lamination and embossing of the composite wearlayer/film to a surface covering substrate. The floor covering product may be a floor tile or a floor covering sheet.
In the preferred process of making the surface covering, the composite is laminated to the substrate on a belt or drum line to form the final product. To deter yellowing of the PVC film, the energy level of the EB radiation is less than 135 KeV with a 2.75 inch average gap. Preferably, the energy level of the EB radiation is no greater than 130 KeV with a 2.75 inch average gap. The preferred dosage to cure the wearlayer composition is about 2 to about 4 Mrad.
In a preferred embodiment, the wear layer composition is formed by reaction of a hydroxyterminated polyester with an isocyanurate in the presence of a multifunctional acrylate. The wear layer composition is cured by the low energy electron beam radiation. The coated decorative rigid film is laminated to a tile base and then cut to form the floor tile product.
Hall U.S. Pat. No. 3,658,620 teaches a method of preparing a sheet capable of being laminated which includes saturating a porous membrane material on both sides with a resin material and subsequently polymerizing the resin with high energy radiation in the form of an electron beam to afford a non-tacky undersurface and a relatively tacky exposed surface. The tacky surface is later used as an adhesive layer. High electron beam dosage (20 Mrad) and accelerating energy (150 to 450 KeV) are required to enable the electrons to penetrate the porous material and cure the impregnated resin to yield a non-tacky surface that can be stripped from a drum. The impregnated porous membrane is laminated to a plywood substrate with the tacky side of the membrane facing the substrate. The final laminar structure is subjected to high energy electron beam to ensure a good mechanical bond between the porous membrane and the substrate.
Williams U.S. Pat. No. 5,401,560 teaches a method for preparing a nonslip floor matte which includes a mineral oxide grit impregnated urethane vinyl layer bonded to a ribbed polyvinyl chloride floor material. The mineral oxide grit resin system is applied to a polyvinyl layer and cured using an electron beam at high electron accelerating energy of 250 to 325 KeV.
The present invention is based on a method of making a surface covering having a PVC film which is precoated with a wearlayer, the wearlayer being cured with low energy electron beam radiation. In the preferred embodiment, the acrylated urethane coated rigid vinyl film is cured with electron beam radiation of less than 135 KeV. The low energy radiation does not yellow the decorative PVC film by the degradation processes commonly observed when a polyvinyl chloride film is subjected to EB radiation. The composite structure is laminated to a continuous sheet of floor covering base under process conditions that yield an aesthetically acceptable composite and then the sheet is cut into floor tile.
xe2x80x9cRigid vinyl filmxe2x80x9d is a term of art which means a polyvinyl chloride film having less than 5 parts plasticizer per hundred parts by weight of resin (phr). Preferably, there is substantially no added plasticizer in the rigid vinyl film.
One object of the invention is to provide a surface covering having a wearlayer/film composite, the wearlayer comprising a composition including a cross-linked organic moiety, the film comprising a vinyl composition, the film having a thickness of no greater than about 20 mils, the wearlayer having been cured with electron beam radiation, and the film having a Delta b of no greater than 2 as measured before and after curing of the wearlayer composition.
Another object of the invention is to provide a surface covering having a wearlayer/film composite, the wearlayer comprising a composition including a cross-linked organic moiety, the wearlayer composition being substantially free of photoinitiator, the film comprising a vinyl composition and having a thickness of no greater than about 20 mils, and the film having a Delta b of no greater than 2 as measured before coating of the wearlayer composition and after curing of the wearlayer composition.
Still another object o the invention is to provide a process of making a surface covering which includes the steps of providing a film of vinyl material, coating the film with a wearlayer composition comprising a cross-linkable organic moiety, and curing the wearlayer composition with electron beam radiation, the electron beam radiation having an energy level of less than that imparted by a 135 KeV field with a 2.75 inch gap.